KI2004wasthe27theditionoftheannualGermanConferenceonArti?cialInt- ligence, which traditionally brings together academic and industrial researchers from all areas of AI and which enjoys increasing international attendance. KI 2004 received 103 submissions from 26 countries. This volume contains the 30 papers that were?nally selected for presentation at the conference. The papers cover quite a broad spectrum of "classical" subareas of AI, like na- ral language processing, neural networks, knowledge representation, reasoning, planning, and search. When looking at this year's contributions, it was exciting to observe that there was a strong trend towards actual real-world applications of AI technology. A majority of contributions resulted from or were motivated by applications in a variety of areas. Examples include applications of pl- ning, where the technology is being exploited for taxiway tra?c control and game playing; natural language processing and knowledge representation are enabling advanced Web-based information processing; and the integration of - sults from automated reasoning, neural networks and machine perception into robotics leads to signi?cantly improved capabilities of autonomous systems. The technical programme of KI 2004 was highlighted by invited talks from outstanding researchers in the areas of automated reasoning, robot planning, constraintreasoning, machinelearning, andsemanticWeb:Jorg · Siekmann(DFKI andUniversityofSaarland, Saarbruc · ken), MalikGhallab(LAAS-CNRS, Toulouse), Franco ı is Fages (INRIA Rocquencourt), Martin Riedmiller (University of - nabru ·ck), andWolfgangWahlster(DFKIandUniversityofSaarland, Saarbruc · ken). Their invited papers are also presented in this volume